Opportunistic measurement and feedback in a wireless local area network

ABSTRACT

Uplink resource assignment in a wireless local area network (WLAN) by an access point (AP) to wireless stations (STAs) is herein provided using opportunistic feedback from the STAs. The AP sends a message to a first STA; the message is also observed by a second STA. Each STA can determine if it wishes to opportunistically send information concerning the message to the AP. The second STA can perform power measurements on the message and send subcarrier signal to noise ratio (SNR) or ranking information to the AP. Thus, the AP can receive, possibly without expectation, encoded or compressed information describing radio channels of the first STA and/or the second STA. Based on the received channel information the AP improves operation of a dynamic resource allocation algorithm which determines uplink grants of resource units (RUs) to the STAs.

PRIORITY APPLICATION

This application claims benefit of U.S. Provisional Patent ApplicationNo. 62/264,719 filed on Dec. 8, 2015 and entitled “OPPORTUNISTICMEASUREMENT AND FEEDBACK IN A WIRELESS LOCAL AREA NETWORK,” which ishereby incorporated by reference herein in its entirety.

FIELD

The described embodiments relate generally to multiple access wirelesscommunications using electronic devices, including systems andtechniques for opportunistically estimating wireless channelcharacteristics between an access point and a first wireless station,and between the access point and a second wireless station.

BACKGROUND

Institute of Electronic and Electrical Engineers (IEEE) standard802.11ac provides an arrangement for channel estimation of uplink anddownlink channels between an access point (AP) and multiple wirelessstations (STAs). The channel estimation involves a process calledsounding. To perform downlink sounding, an AP transmits a Null DataPacket-Announcement (NDP-A). The NDP-A contains the addresses ofparticular STAs to which the AP wishes to transmit data. The NDP-A isfollowed by a Null Data Packet (NDP). The NDP represents pilot energy;that is, a pre-defined pattern. Each STA addressed by the NDP-A measuresthe downlink wireless channel from the AP to itself. The channelmeasurement is possible because the given STA knows the pre-definedpattern and can estimate the effects of the channel on that pattern (forexample, amplitude attenuation, carrier phase rotation, and time delay).Uplink sounding can be performed by instructing one or more STAs to sendNDPs, which the AP then observes.

IEEE 802.11n specifies a high throughput (HT) physical layer and mediumaccess control layer. IEEE 802.11ac specifies a very high throughput(VHT) physical layer and medium access control layer. More informationcan be found in IEEE P802.11 Wireless LANS, Specification Framework forTGax, Nov. 25, 2015, doc.: IEEE 802.11-15/0132r10.

For downlink channel measurements, various STAs feedback their channelmeasurements to an AP and an AP with multiple antennas can transmitmultiple streams to the multiple STAs (each with multiple antennas)based on the received channel information.

Wireless Local Area Networks (WLANs) supporting uplink and downlinktransmission between multiple STAs and APs rely on accurate channelinformation. An AP may have many STAs desiring service, with differentradio channels to each STA due to unique scattering geometries betweenthe AP and each STA. A conventional AP can allocate bandwidth of anuplink transmission to a STA that has a weak uplink channel to the AP.Other STAs will not be scheduled to transmit, and the overall systemthroughput is low.

SUMMARY

Representative embodiments set forth herein disclose various systems andtechniques for opportunistically estimating wireless channelcharacteristics between an access point and a first wireless station,and between the access point and a second wireless station. Embodimentscan be implemented to provide various advantages, including improvingdetermination of uplink channel information from multiple STAs, whichcan provide for improved allocation of uplink radio resources by the AP.

WLAN systems include APs and STAs. The embodiments provided hereininclude providing observed downlink channel information from STAs to anAP. In configurations in which the AP can estimate the uplink channelbased on the downlink channel (e.g., when a channel reciprocity propertyapplies) the AP can improve uplink channel allocation based on thereceived observations of downlink channel transmission.

In order to efficiently allocate uplink resources to multiple STAs, anestimate of a joint uplink channel matrix H with submatrix components H₁and H₂ is provided by embodiments of this disclosure. The AP can solicitobservations from STAs or receive unsolicited channel information fromSTAs. The AP then applies an algorithm based on the channel informationto determine which STAs should be allocated uplink resources in a giventime interval. The STAs can provide different representations of channelinformation and the information can be sent flexibly in a number ofdifferent message types.

This Summary is provided merely for purposes of summarizing some exampleembodiments so as to provide a basic understanding of some aspects ofthe subject matter described herein. Accordingly, it will be appreciatedthat the above-described features are merely examples and should not beconstrued to narrow the scope or spirit of the subject matter describedherein in any way. Other features, aspects, and advantages of thesubject matter described will become apparent from the followingDetailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The included drawings are for illustrative purposes and serve to provideexamples of possible structures and arrangements for the disclosedsystems and techniques, e.g., for intelligently and efficiently managingcalls and other communications between multiple associated user devices.These drawings in no way limit any changes in form and/or detail thatmay be made to the embodiments by one skilled in the art withoutdeparting from the spirit and scope of the embodiments. The embodimentswill be readily understood by the following detailed description inconjunction with the accompanying drawings, wherein like referencenumerals designate like structural elements.

FIG. 1 illustrates an exemplary WLAN system including an AP and multipleSTAs, according to some embodiments.

FIG. 2 illustrates an exemplary message sequence in which two STAsopportunistically provide feedback channel estimation, according to someembodiments.

FIG. 3 illustrates an exemplary message sequence in which an AP requestsa channel estimate from a STA, according to some embodiments.

FIG. 4 illustrates an exemplary message sequence in which a STAopportunistically provides a channel estimate in a medium access control(MAC) header, according to some embodiments.

FIG. 5 illustrates an exemplary message sequence in which a STAopportunistically provides a channel estimate in a management frame,according to some embodiments.

FIG. 6 illustrates an exemplary message sequence in which a STAopportunistically provides a channel estimate in a control frame,according to some embodiments.

FIG. 7 illustrates an exemplary message sequence in which the APstimulates transmission of null data packets by STAs in order toinitiate explicit uplink channel measurement, according to someembodiments.

FIG. 8 illustrates an exemplary message sequence in which an AP sends anull data packet and then a trigger frame to collect feedback from STAs,according to some embodiments.

FIG. 9 illustrates exemplary measurements of channel responses at OFDMtone positions corresponding to particular resource units (RUs) in afrequency spectrum, according to some embodiments.

FIG. 10 illustrates an exemplary logic flow for a first STA, accordingto some embodiments.

FIG. 11 illustrates an exemplary logic flow for an AP, according to someembodiments.

FIG. 12 illustrates an exemplary apparatus for implementation ofembodiments disclosed herein.

DETAILED DESCRIPTION

Representative applications of apparatuses, systems, and methodsaccording to the presently described embodiments are provided in thissection. These examples are being provided solely to add context and toaid in the understanding of the described embodiments. It will thus beapparent to one skilled in the art that the presently describedembodiments can be practiced without some or all of these specificdetails. In other instances, well known process steps have not beendescribed in detail in order to avoid unnecessarily obscuring thepresently described embodiments. Other applications are possible, suchthat the following examples should not be taken as limiting.

In order to implement Multi-User, Multiple Input, Multiple Output(MU-MIMO) on an uplink, it is useful to determine channel informationbetween a set of STAs that will transmit together (e.g., in the sametime interval) to the AP. In some embodiments, to obtain multiplereceived streams with good signal to noise ratio at the receiver, the APwill compute transmission parameters based on a decomposition of a jointchannel matrix H, where H represents uplink channel information fromeach STA scheduled to transmit in a same time interval. H can beestimated at the AP.

Particular aspects of the embodiments are now discussed with referenceto the figures.

Communication System

FIG. 1 illustrates an exemplary WLAN system including STA 102, STA 104,AP 110, and Internet 120. The wireless connection between STA 102 and AP110 is indicated as link 106 and the connection between STA 104 and AP110 is indicated as link 108. The direction or sense of theseconnections is described as follows. Transmission from AP 110 to theSTAs is downlink transmission. Transmission from either STA to AP 110 isuplink transmission. In some embodiments, uplink and downlinktransmissions use different frequency bands. In that case, the channelresponse on the downlink from AP 110 to STA 102, for example, may differfrom the channel response on the uplink from STA 102 to AP 110, e.g.,because of the different path lengths and/or signal characteristics. Achannel response is based on the phenomenon of radio waveforms at thedownlink or uplink frequency interacting with scatterers. When uplinkand downlink frequencies differ, a given waveform at the uplinkfrequency can experience a different total carrier phase rotationaccumulated in interacting with a set of scatterers than a waveform atthe downlink frequency interacting with the same set of scatterers.Attenuation generally also is a function of frequency. In someembodiments, uplink and downlink transmissions use the same frequencyband. When uplink and downlink transmissions are on the same band(s),the principle of channel reciprocity implies that the channel responseon the downlink from AP 110 to STA 102, for example, should be the sameas the channel response on the uplink from STA 102 to AP 110.

An OFDM system uses a plurality of subcarriers; let the number ofsubcarriers in an OFDM symbol be L. Generally the uplink channel fromSTA 102, H₁, is an L-vector formed of L complex scalars, each scalarrepresenting a channel gain at the corresponding subcarrier. For somedelay spread and subcarrier spacings of interest, H₁ changes slowly inresponse to frequency differences from element to element of H₁, and itis not necessary to perform a measurement at each subcarrier. Forexample, measurements can be made at subcarriers indexed with an evenindex value, and the values of H₁ corresponding to the odd indices canbe estimated by interpolating between the values of H₁ at the evenindices. AP 110 can also learn the uplink channel response, H₂,associated with link 108, e.g., by asking STA 104 to send an NDP datapacket as described below. The joint matrix H may be written as H=[H₁H₂] and an observation at one antenna of the AP may be written asy=H′[x₁′ x₂′]′ (neglecting noise) where x is a transmit vector and z′ isthe Hermitian transpose of z. Many symbolic representations arepossible. Let two antennas at the AP be labelled A and B. The twoobservations may be written y_(A)=H_(A)′[x₁′ x₂′]′ and y_(B)=H_(B)′[x₁′x₂′]′. In the two antenna-AP case, H₁, the uplink channel from STA 102to AP 110, generalizes to H_(1A) and H_(1B). Expressions in terms ofmore than two antennas at the AP are straightforward. Particular detailsof OFDM modulation, such as subcarriers, will be touched on as needed inthe explanations of the channel sounding techniques provided herein.

Dynamic Resource Allocation for Uplink

In some embodiments, AP 110 executes a dynamic resource allocationalgorithm in order to maximize the total transfer of information on theuplink for multiple devices attempting to access a shared resource (thebandwidth available for transmission). In a bandwidth distributionsolution of information theory known as water-filling, the multipleaccess channel reaches a high throughput when the channel users with thebest channels devote the most energy to the channel. To identify whichSTAs have the best channels and thus should transmit the most bits in agiven time, AP 110 needs to learn (or assess) the channel. When AP 110has adequate information from STAs of interest, it can run its dynamicchannel allocation algorithm and allocate multiple access resources,such as OFDM RUs to various STAs according to a configuration determinedby the algorithm.

Uplink Channel Estimate, Opportunistic STA Feedback

FIG. 2 illustrates an exemplary message sequence that results in the AP110 obtaining an estimate of the uplink channels H₁ and H₂. Threetimelines (203, 213, and 223) are shown in FIG. 2, one for each of AP110, STA 102 and STA 104 (indicated in parentheses in FIG. 2). The threetimelines illustrate transmitted signals (for example, the variables x₁and/or x₂ as explained with respect to FIG. 1); corresponding receivedversions of the transmitted signals (for example, the variable y asexplained with respect to FIG. 1) are shown as data 202-R1 and data202-R2. Generally, the received versions of signals are not shown inthese figures. In FIG. 2, uplink channel information is collected in atime sequence. The first event occurs on timeline 203. AP 110 sends data202 addressed to STA 102. STA 102 receives data 202 (indicated withdashed box data 202-R1) and responds by transmitting blockacknowledgement BA 210. STA 102 also sends an estimate of downlinkchannel H₁ as feedback information FB 212. FB 212 can be a frame with aMAC header and MAC payload, or it can be, for example, a managementframe. STA 102 creates FB 212 based on its observation of data 202. Thechannel information sent by STA 102 in FB 212 is encoded in somefashion. The channel information may be signal to noise ratio (SNR)information per subcarrier, received signal strength indication (RSSI)information for an entire modulated bandwidth, or, for example, aranking of strongest subcarriers or RUs observed in data 202 by STAs 102and/or 104.

The channel information may be extensive, such as per subcarrier or perRU. The value of each SNR value, for example, may be precise such as 8bits, or may be quantized using a lower number of bits, such as 1, 2, 3,or 4 bits. The number of subcarriers or number of RUs represented may beextensive, such as approximately 256 subcarriers in 20 MHz or 9 RUs.Alternatively, the number of subcarriers (or RUs) represented may be asampling, such as 10, 20 or 50 subcarriers in 20 MHz. In someembodiments, the channel information may include a ranking withoutintensity or power or signal to noise ratio information. For example,STA 102 may provide an indication of the strongest observed subcarrieror RU. In some embodiments, this indication is an index or address ofthe indicated subcarrier or RU. In some embodiments, STA 102 providesindications of a strongest N subcarriers or strongest M RUs. Forexample, M can be 3 indicating the strongest 3 RUs. N can be 4indicating the strongest 4 subcarriers. In some embodiments, STA 102provides a single global power measurement, such as an amount of powerobserved over a time interval in a certain bandwidth, for example, 20MHz. This power measurement can be an RSSI value encoded with highresolution (for example 8 bits) or roughly quantized (for example: 1, 2,3, or 4 bits).

In some embodiments, STA 102 provides channel information concerning,e.g., approximately one half of the RUs in a given bandwidth. Forexample, STA 102 can provide information about four or five RUs of nineRUs in a 20 MHz bandwidth. In some embodiments, STA 102 provides 3 or 4bit SNR values for the highest quality observed RUs observed. Thelocation or identity of the RUs for which information is provided by theSTA can be identified using indices.

In some embodiments, STA 102 ranks 9 RUs observed in 20 MHz and sendsthe ordered list determined by the ranking to AP 110. Such atransmission could be realized using four bits per RU index for nineRUs, thus a maximum number of bits needed would be four times nine or 36bits. Other encoding schemes could be used by STA 102 to indicate theordered list to AP 110. The ranking and/or the RSSI information, in someembodiments, can be sent by STA 102 to AP 110.

After receiving the channel information, AP 110 can use it to decidewhich STA to schedule for a next uplink physical layer convergenceprotocol (PLCP) protocol data unit (PPDU) transmission opportunity andwhich RU or RUs should be allocated to that STA.

AP 110, in some embodiments, estimates uplink channel H₁ from STA 102 asbeing equal to the downlink channel from AP 110 to STA 102. Thisassumption is strong when AP 110 and STA 102 operate, for example, in atime division duplex (TDD) manner of some kind on a common frequencyband; this may be referred to as the TDD assumption (see discussion ofreciprocity above). In some embodiments, TDD does not impose a stricttime slot structure. STA 104 may also observe data 202 and decide toopportunistically transmit a channel estimate to AP 110; STA 104'sobservation is indicated in FIG. 2 as a dashed box marked data 202-R2.STA 104 may obtain a downlink channel estimate based on known components(e.g., pre-determined bit or symbol values) of a header or preamble inthe frame indicated as data 202 in FIG. 2. A channel estimate may alsobe referred to as a channel quality herein. In some embodiments, STA 104produces channel information based on power observations and notintensity. In that case, STA 104 does not need knowledge of componentsof data 202. An example of such a data-value-insensitive measurement isRSSI. Thus, in FIG. 2, an exemplary transmission FB 220 from STA 104provides AP 110 with information about the downlink channel from AP 110to STA 104. AP 110 can estimate (e.g., under the TDD assumption) uplinkchannel H₂ from STA 104 as being equal to the downlink channel from AP110 to STA 104. In FIG. 2, STAs 102 and 104 provided feedbackinformation opportunistically. This information is useful and can alsobe used by AP 110 in its dynamic resource allocation algorithm to selectwhich STAs should be granted uplink resources for a given time intervaland the number of RUs to be granted to each selected STA.

Uplink Channel Estimate, Solicited STA Feedback

Alternatively or additionally, in some embodiments, AP 110 can solicitSTA feedback. FIG. 3 illustrates an exemplary implementation in which AP110 sends channel estimate request (FB request) 302 after receiving theblock acknowledgement BA 210. FB request 302 can be implemented with anydesired fields, such as a feedback control field and an address field.Alternatively, STA options can be implied by a standard specificationset of policies or rules; thus, an explicit feedback control field, insome embodiments, is not included in FB request 302. The feedbackcontrol field can be asserted (for example, set to “11” as an examplefeedback control field value) to indicate the feedback is required. Theaddress field can be used to indicate a specific STA or a group of STAs,or can be omitted or unused for some values of the control field. Insome embodiments, the feedback control field has a soft aspect, that is,the control field indicates that feedback is permitted, but not required(an exemplary value may be “10”). If the feedback control field is notasserted, this can indicate that feedback is discouraged (an exemplaryvalue “01”) or not permitted (an exemplary value “00”). AP 110 may sendsuch a request under several scenarios. In some embodiments AP 110 candetermine that more channel information about the uplink channel fromSTA 102 would improve its dynamic resource allocation algorithm. Toobtain this information, it can request feedback from STA 102. STA 102,in some embodiments, evaluates the feedback control field to arrive at areporting decision. When STA 102 arrives at a positive reportingdecision and responds with an estimate of the downlink channel (thisestimate is included in message FB 312), AP 110 can approximate theuplink channel as being equal to the downlink channel. STA 102, in someembodiments retains recent reporting decision outcomes in a reportingrecord.

In some scenarios, AP 110 serves many STAs and at some times has channelinformation with high confidence (low error variance on the channelestimates) for the STAs with active links. In this case, AP 110 mayrefrain from soliciting feedback, since the feedback event occupies afinite portion of the available channel bandwidth. In such a case, thefeedback control field of FB request 202 may have value “00”, and STA102 would send BA 210 but not FB 312. In some embodiments, the feedbackcontrol field and address field can be sent in a header of data 202. Inthat case, in some embodiments, FB request 302 need not be sent and STA102 will still receive the feedback control field and can actaccordingly. STA 102, in some embodiments, can behave as follows: i)transmit FB 312 based on a corresponding request for feedback (e.g.,feedback control field of data 202 having value “11”), ii) transmit FB312 based on a field encouraging feedback (e.g., feedback control field“10”), iii) transmit FB 312 despite a field discouraging feedback (e.g.,feedback control field “01”), iv) not transmit FB 312 based on a fieldprohibiting feedback (e.g., feedback control field “00”) v) optionallynot transmitting FB 312 based on the feedback control field value “10”,or vi) optionally not transmitting FB 312 based on the feedback controlfield value “01.”

FIGS. 4-6 illustrate flexible approaches by which a STA, e.g., STA 102,can provide an encoding of downlink channel information to AP 110.

PPDU, Management Frames and Control Frames

FIG. 4 includes an illustration of an exemplary MAC header embodiment. Atransmission by an AP or by a STA can include a PPDU. A MAC PPDU canhave a header and a payload. The header can be a MAC header. The payloadcan be a MAC payload. FIG. 4 illustrates a control field 414 in a MACheader 412. MAC header 412 is followed by MAC payload 416. Control field414 can include a compressed version of a downlink channel estimate. STA102 performs a channel estimate based on its observation of data 202.The encoding can be done in a fashion similar to that in FB 212 or FB220 of FIG. 2. For example, SNR and/or RSSI may be encoded with variouslevels of quantization. A ranking of RUs may be sent. In someembodiments, opportunistic feedback FB 212 (or FB 220) of FIG. 2 can beor can include a MAC header 412 with a control field 414.

FIG. 5 illustrates an exemplary management frame in which opportunisticfeedback FB 212 (or FB 220) of FIG. 2 comprises a management frame 502.A management frame sent by STA 102 (or STA 104), in some embodiments, isnot scheduled by AP 110. AP 110 may not know when management frame 502will be transmitted by STA 102. The time axis 213 in FIG. 5 is shownbroken with an indication that STA 102 may perform other activities andsome time can pass before transmission of management from 502.Consequently, the channel may be busy when management frame 502 is sent,and a collision can occur with a transmission from AP 110 or STA 104,for example. The management frame 502 can be sent with an immediate ACKpolicy. If AP 110 successfully decodes management frame 502 and animmediate ACK policy is indicated in management frame 502, AP 110, insome embodiments, responds with ACK 510. STA 102 receives ACK 510 andthen does not re-transmit the encoded channel information of managementframe 502. When STA 102 does not receive an ACK after transmission ofthe management frame, it can retransmit the information of managementframe 502. In some embodiments, management frame 502 is sent with a noACK policy. In that case, AP 110 need not send ACK 510 and STA 102 neednot wait for an ACK before continuing with other uplink data to be sent.In some embodiments, AP 110 sends a FB request in a management frame andexpects STA 102 to respond with channel information in a managementframe.

FIG. 6 illustrates an exemplary channel feedback embodiment in whichsolicited feedback FB 312 of FIG. 3 comprises a control frame 612. Acontrol frame to be sent by STA 102 is scheduled by AP 110 using FBrequest 602; that is, FB request 602 can include a control frame sent byAP 110. In some embodiments, FB request 602 polls OFDMA RU qualityinformation from STA 102. AP 110 expects control frame 612 to betransmitted by STA 102 in a limited forthcoming time interval as shownin FIG. 6. In some embodiments, the time interval is a short interframespace (SIFS).

NDP-A Examples

FIG. 7 illustrates an exemplary AP-initiated uplink (UL) measurementusing a null data packet-announce (NDP-A) message 702. In someembodiments described herein, AP 110 learns the uplink channel response,H₁, associated with link 106 by asking STA 102 to send a pilot orsounding or null data packet (NDP) signal on the uplink. AP 110 thensamples the NDP arriving from STA 102. Because AP 110 knows the NDPwaveform sent by STA 102, it can estimate the channel H₁, for example,using a correlation function. With regard to the discussion of FIG. 1,x₁ in the FIG. 7 case of pilot transmission is the NDP waveform, and sox₁ is known to AP 110 before it is sent by STA 102. In some embodiments,NDP-A 702 instructs STA 102 to energize particular ones of the RUs ofthe uplink channel frequency band with pilot energy. The location of theenergized pilots can be referred to as a map. The instruction of NDP-A702 includes an OFDMA RU allocation. NDP-A indicates a different OFDMARU allocation to be used by STA 104. In embodiments, the intersection ofpilot energy locations of the resulting NDP 710 map and the resultingNDP 720 map shows no common subcarriers in use at a given OFDM symboltime. Thus NDP 710 and NDP 720 are frequency division multiplexed (seeFIGS. 7 and 9) at the RU level in some embodiments. FIG. 7 indicates thetransmissions from STA 102 and STA 104 are Multi-User (MU) multiplexed.This MU multiplexing is from the point of view of AP 110. AP 110estimates the uplink channels H₁ and H₂ based on a composite receivedsignal (the variable y discussed with respect to FIG. 1). The compositereceived signal is based on H₁, H₂, NDP 710 and NDP 720. Subsequently,AP 110 can send a trigger message (not shown), which can includemulti-user transmit parameters, and thus AP 110 will schedule thetransmission of data by STA 102 and STA 104.

FIG. 8 illustrates an exemplary AP-initiated DL-measurement-based ULestimate using an NDP-A 702, NDP 802 and trigger message 804. Inparticular, FIG. 8 illustrates an exemplary embodiment to estimate theuplink channels from STA 102 and STA 104 based on first obtainingdownlink channel information from STA 102 and STA 104. The uplinkchannels can be approximated by AP 110 based on the downlink channelestimates using the TDD assumption/reciprocity as described above. STAs102 and 104 receive NDP-A 702 and then await NDP 802. STA 102 estimatesits downlink channel based on sampling NDP 802 as received at STA 102.STA 104 estimates its downlink channel based on sampling NDP 802 asreceived at STA 104. AP 110 then transmits trigger 804 addressed to STAs102 and STA 104. STAs 102 and 104 respond with channel estimate messagesFB 812 and FB 822 respectively. AP 110 estimates uplink channels H₁ andH₂ based on information in FB 812 and FB 822, respectively. The waveformversions of FB 812 and FB 822 received at AP 110 are also generally afunction of the uplink channels H₁ and H₂ since FB 812 travels throughat least some subcarriers of H₁ and FB 822 travels through at least somesubcarriers of H₂, in some embodiments.

RU Description and Quality Measures

Further description of RUs and channel information is provided in FIG.9. FIG. 9 illustrates an available system bandwidth of 20 MHz (althoughother bandwidths can be used in other implementations). Each STA that isprovided with an uplink transmission grant is assigned one or more RUson which to transmit. The duration of the subsequent data transmissionfrom a STA, in some instances, will be for one PPDU, that is, one packetinterval. An example downlink PPDU is data 202. An RU, in someembodiments, represents 26 contiguous tones or subcarriers (althoughother arrangements of tones or subcarriers can be used). For example,STA 102 of FIG. 1 may be provided with an allocation representing eachof RU 921, 922, . . . , 929, that is, the entire 20 MHz band. In someembodiments, STA 102 is provided RU 921, a STA 103 (not shown) isprovided RU 922 and STA 104 of FIG. 1 is provided RU 929. In someembodiments, STA 102 is provided with RU 921 and STA 104 is providedwith RU 922 and RU 924. The allocations of one or more RUs to aparticular STA need not be contiguous in frequency.

FIG. 9 illustrates allocations 921 . . . 929 representing ninetwenty-six-tone RUs in a 20 MHz system bandwidth. In order to learnwhich RUs to assign to which STAs, the AP can collect information usingone or more of the implementations described above with regard to FIGS.2-8. FIG. 9 illustrates that STA 102 may observe tones 912, . . . , 914,. . . , and 992 and produce exemplary quality measures indicated asSNR₁, . . . , SNR₉ or rank₁, . . . , rank₉. These quality measures arereported, for example, as encodings described with regard to feedbackmessage FB 212, FB 220, FB 312, FB 812 or, for example, FB 822 describedabove. The transmission of the encoded information can be performedaccording to the frame types discussed with respect to one or more ofFIGS. 4-6 and FIG. 8. In some embodiments, one report contains qualityvalues for multiple RUs and these RUs can be based on certain criteria,for example the top three RUs that have the best SNR values. In someembodiments, the RU allocations 921 . . . 929 (shown in FIG. 9) havevalues assigned to the variables rank₁, . . . , rank₉. For example (seeTable 1), these 9 rank values (rank₁, . . . , rank₉) may have exampleranks of {5,2,9,6,4,8,1,3,7} where 1 indicates the highest SNR out ofthe set SNR₁, . . . , SNR₉ and 9 represents the lowest (noisiest) SNRout of the set. If the top 3 SNR values are to be sent, then, in thisexample, SNR₇ (strongest), SNR₂ (second strongest), and SNR₈ (thirdstrongest) will be sent in the report.

TABLE 1 Rank Example RU Index Rank SNR Value 921 5 SNR₁ 922 2 SNR₂ 923 9SNR₃ 924 6 SNR₄ 925 4 SNR₅ 926 8 SNR₆ 927 1 SNR₇ 928 3 SNR₈ 929 7 SNR₉

The reporting message, in some embodiments, includes indications of thetop-ranked RU indices without sending indications of the correspondingSNR values. In the example of Table, in some embodiments, the reportingmessage would thus indicate indices 927, 922, and 928 without reportingSNR₇, SNR₂ or SNR₈.

In other embodiments, a system bandwidth of 40 MHz is available foruplink transmission—corresponding to eighteen twenty-six-tone RUs. In a40 MHz bandwidth, the AP can request that up to eighteen STAs respondwith NDPs in order that the AP may determine up to 18 allocations.

FIG. 10 illustrates an exemplary logic flow realized in some embodimentsby a wireless device. At 1002, the wireless device receives a firstmessage from a base station. At 1004, the wireless device determines areporting decision. The wireless device can favor a reporting decisionif: i) a buffer status in the wireless device indicates a buffer hasdata to be sent or is about to overflow, ii) an estimate of a geographicmobility of the first device indicates that the uplink channel ischanging rapidly and a base station should be updated, iii) in responseto a feedback control field received from the base station, iv) ameasure of overall network activity in uplink and downlink by thewireless device, and/or v) an estimate of arrival rate of received dataat the wireless device. In some embodiments, the overall networkactivity is a cumulative value including a sum of the uplink activity(in terms of transmitted packet rate) and downlink activity (in terms ofreceived packet rate).

When the reporting decision is negative, indicated by 1005, the wirelessdevice waits for a next message at 1007. When the reporting decision ispositive, indicated by 1006, the wireless device obtains a channelestimate at 1008; in some embodiments this could be an SNR value,ranking value, RU index, and/or RSSI value. The channel estimate couldbe in memory, or it could be computed by the STA based on a message,such as the first message. At 1010, the wireless device formats a secondmessage with an encoding of the channel estimate. At 1012, the wirelessdevice sends the second message to the base station. A STA is an exampleof a wireless device and an AP is an example of a base station.

FIG. 11 illustrates an exemplary logic flow realized in some embodimentsby a base station. At 1102, the base station sends a message to a firstwireless device. At 1104, the base station receives a first channelestimate (e.g., an SNR value, ranking value, RU index, and/or RSSIvalue) based on the message. At 1106, the base station receives a secondchannel estimate (e.g., an SNR value, ranking value, RU index, and/orRSSI value) based on the message. At 1108, the base station allocates amultiple access resource, for example, an OFDMA RU, to the firstwireless device or to the second wireless device. 1108 also indicatesthat transmissions of the first and second channel estimates by thefirst and second wireless devices, respectively, were not scheduled bythe base station. A STA is an example of a wireless device and an AP isan example of a base station.

Wireless devices, and mobile devices in particular, can incorporatemultiple different radio access technologies (RATs) to provideconnections through different wireless networks that offer differentservices and/or capabilities. A wireless device can include hardware andsoftware to support a wireless personal area network (“WPAN”) accordingto a WPAN communication protocol, such as those standardized by theBluetooth® special interest group (“SIG”) and/or those developed byApple referred to as an Apple Wireless Direct Link (AWDL). The wirelessdevice can discover compatible peripheral wireless devices and canestablish connections to these peripheral wireless devices located inorder to provide specific communication services through a WPAN. In somesituations, the wireless device can act as a communications hub thatprovides access to a wireless local area network (“WLAN”) and/or to awireless wide area network (“WWAN”) to a wide variety of services thatcan be supported by various applications executing on the wirelessdevice. Thus, communication capability for an accessory wireless device,e.g., without and/or not configured for WWAN communication, can beextended using a local WPAN (or WLAN) connection to a companion wirelessdevice that provides a WWAN connection. Alternatively, the accessorywireless device can also include wireless circuitry for a WLANconnection and can originate and/or terminate connections via a WLANconnection. Whether to use a direct connection or a relayed connectioncan depend on performance characteristics of one or more links of anactive communication session between the accessory wireless device and aremote device. Fewer links (or hops) can provide for lower latency, andthus a direct connection can be preferred; however, unlike a legacycircuit-switched connection that provides a dedicated link, the directconnection via a WLAN can share bandwidth with other wireless devices onthe same WLAN and/or with the backhaul connection from the access pointthat manages the WLAN. When performance on the local WLAN connectionlink and/or on the backhaul connection degrades, a relayed connectionvia a companion wireless device can be preferred. By monitoringperformance of an active communication session and availability andcapabilities of associated wireless devices (such as proximity to acompanion wireless device), an accessory wireless device can requesttransfer of an active communication session between a directionconnection and a relayed connection or vice versa.

In accordance with various embodiments described herein, the terms“wireless communication device,” “wireless device,” “mobile device,”“mobile station,” “wireless station”, “wireless access point”,“station”, “access point” and “user equipment” (UE) may be used hereinto describe one or more common consumer electronic devices that may becapable of performing procedures associated with various embodiments ofthe disclosure. In accordance with various implementations, any one ofthese consumer electronic devices may relate to: a cellular phone or asmart phone, a tablet computer, a laptop computer, a notebook computer,a personal computer, a netbook computer, a media player device, anelectronic book device, a MiFi® device, a wearable computing device, aswell as any other type of electronic computing device having wirelesscommunication capability that can include communication via one or morewireless communication protocols such as used for communication on: awireless wide area network (WWAN), a wireless metro area network (WMAN)a wireless local area network (WLAN), a wireless personal area network(WPAN), a near field communication (NFC), a cellular wireless network, afourth generation (4G) LTE, LTE Advanced (LTE-A), and/or 5G or otherpresent or future developed advanced cellular wireless networks.

The wireless device, in some embodiments, can also operate as part of awireless communication system, which can include a set of clientdevices, which can also be referred to as stations, client wirelessdevices, or client wireless devices, interconnected to an access point(AP), e.g., as part of a WLAN, and/or to each other, e.g., as part of aWPAN and/or an “ad hoc” wireless network, such as a Wi-Fi directconnection. In some embodiments, the client device can be any wirelessdevice that is capable of communicating via a WLAN technology, e.g., inaccordance with a wireless local area network communication protocol. Insome embodiments, the WLAN technology can include a Wi-Fi (or moregenerically a WLAN) wireless communication subsystem or radio, the Wi-Firadio can implement an Institute of Electrical and Electronics Engineers(IEEE) 802.11 technology, such as one or more of: IEEE 802.11a; IEEE802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012;IEEE 802.11ac; IEEE 802.11ax; or other present or future developed IEEE802.11 technologies.

IEEE 802.11ac is an example of a system using Orthogonal FrequencyDivision Multiplexing (OFDM) to modulate data onto OFDM symbols. OFDM isa modulation scheme which uses many narrowband subcarriers to overcomedelay spread yet provide high bandwidth. A modulation feature of an OFDMsymbol known as a cyclic prefix reduces the need or complexity ofequalization of multipath effects at a receiver in many scenarios. Thedistribution of subcarriers within a single OFDM symbol among more thanone user is known as Orthogonal Frequency Division Multiple Access(OFDMA). A collection of subcarriers within an OFDM symbol can bereferred to as a resource unit (RU). In an OFDMA frame structure, eachsubcarrier is modulated with a number of OFDM symbols. On a givensubcarrier during a given frame, some RUs may be devoted to pilot energyand other RUs may be provided with no pilot energy. The collection ofRUs over all the subcarriers is represented by a time/subcarrier map. Anull data packet (NDP) comprises pilot tones useful for channelestimation.

Additionally, it should be understood that the wireless devicesdescribed herein may be configured as multi-mode wireless communicationdevices that are also capable of communicating via different thirdgeneration (3G) and/or second generation (2G) RATs. In these scenarios,a multi-mode wireless device or UE can be configured to preferattachment to LTE networks offering faster data rate throughput, ascompared to other 3G legacy networks offering lower data ratethroughputs. For instance, in some implementations, a multi-modewireless device or UE may be configured to fall back to a 3G legacynetwork, e.g., an Evolved High Speed Packet Access (HSPA+) network or aCode Division Multiple Access (CDMA) 2000 Evolution-Data Only (EV-DO)network, when LTE and LTE-A networks are otherwise unavailable.

Representative Exemplary Apparatus

FIG. 12 illustrates in block diagram format an exemplary computingdevice 1200 that can be used to implement the various components andtechniques described herein, according to some embodiments. Inparticular, the detailed view of the exemplary computing device 800illustrates various components that can be included in STA 102, STA 104or AP 110 illustrated in FIG. 1. As shown in FIG. 12, the computingdevice 1200 can include a processor 1202 that represents amicroprocessor or controller for controlling the overall operation ofcomputing device 1200. The computing device 1200 can also include a userinput device 1208 that allows a user of the computing device 1200 tointeract with the computing device 1200. For example, the user inputdevice 1208 can take a variety of forms, such as a button, keypad, dial,touch screen, audio input interface, visual/image capture inputinterface, input in the form of sensor data, etc. Still further, thecomputing device 1200 can include a display 1210 (screen display) thatcan be controlled by the processor 1202 to display information to theuser (for example, information relating to incoming, outgoing, or activecommunication session). A data bus 1216 can facilitate data transferbetween at least a storage device 1240, the processor 1202, and acontroller 1213. The controller 1213 can be used to interface with andcontrol different equipment through an equipment control bus 1214. Thecomputing device 1200 can also include a network/bus interface 1211 thatcouples to a data link 1212. In the case of a wireless connection, thenetwork/bus interface 1211 can include wireless circuitry, such as awireless transceiver and/or baseband processor.

The computing device 1200 also includes a storage device 1240, which cancomprise a single storage or a plurality of storages (e.g., harddrives), and includes a storage management module that manages one ormore partitions within the storage device 1240. In some embodiments,storage device 1240 can include flash memory, semiconductor (solidstate) memory or the like. The computing device 1200 can also include aRandom Access Memory (“RAM”) 1220 and a Read-Only Memory (“ROM”) 1222.The ROM 1222 can store programs, utilities or processes to be executedin a non-volatile manner. The RAM 1220 can provide volatile datastorage, and stores instructions related to the operation of thecomputing device 1200.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium. The computer readable medium is any datastorage device that can store data which can thereafter be read by acomputer system. Examples of the computer readable medium includeread-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape,hard storage drives, solid state drives, and optical data storagedevices. The computer readable medium can also be distributed overnetwork-coupled computer systems so that the computer readable code isstored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

What is claimed is:
 1. A method comprising: by a wireless device:receiving a first message from a second wireless device; determining tosend a report of a channel estimate; determining a first channelestimate based on the first message; formatting a second message with anencoded value, wherein the encoded value is based on the first channelestimate; and sending the second message to the second wireless device.2. The method of claim 1, further comprising: determining a first set ofquality measures, each quality measure of the first set corresponding toa resource unit (RU) of a second set of RUs; ranking the first set, toform a third set of rank values; choosing, based on the third set, asubset of the first set, wherein: i) the subset has the highest qualitymeasure values among the first set and ii) the subset comprises anindication of RU indices; and including a quality indication in thesecond message, wherein: i) the quality indication includes the encodedvalue, and ii) the encoded value corresponds to an encoding of one ormore of the RU indices in the subset.
 3. The method of claim 1, whereinthe determining to send a report of a channel estimate is performedbased on one or more of: i) a buffer status in the wireless device, ii)an estimate of a geographic mobility of the wireless device, iii) avalue of a feedback control field in the first message, iv) an estimateof a cumulative network activity of the wireless device, and/or v) anestimate of an arrival rate of received data at the wireless device. 4.The method of claim 1, wherein the determining to send a report of achannel estimate is performed based on a value of a feedback controlfield in the first message.
 5. The method of claim 1, wherein theencoded value represents a channel quality of one or more resource units(RUs), the channel quality corresponding to a signal to noise ratio(SNR) or a ranking.
 6. The method of claim 1, wherein the encoded valuerepresents a received signal strength indication (RSSI) computed over asystem bandwidth.
 7. The method of claim 1, wherein the first message isnot address to the wireless device.
 8. The method of claim 1, whereinthe wireless device and the second wireless device comply with anInstitute of Electronic and Electrical Engineering (IEEE) Wireless LocalArea Network (LAN) standard.
 9. The method of claim 8, wherein thesecond message comprises a Medium Access Control (MAC) header thatincludes the encoded value.
 10. The method of claim 9, wherein thesecond message further comprises a MAC payload.
 11. The method of claim10, wherein the second message comprises a management frame, themanagement frame comprises a MAC header, and the MAC header comprisesthe encoded value.
 12. The method of claim 11, wherein the secondmessage indicates an immediate acknowledgement (ACK) policy.
 13. Themethod of claim 8, wherein the second message comprises a control framethat includes the encoded value.
 14. A wireless device comprising: atransceiver; a memory; and a processor, wherein the memory comprisesinstructions that when executed by the processor cause the wirelessdevice to perform steps comprising: receiving, via the transceiver, afirst message from a second wireless device; determining to send areport of a channel estimate; determining a first channel estimate basedon the first message; formatting a second message with an encoded value,wherein the encoded value is based on the first channel estimate; andsending, via the transceiver, the second message to the second wirelessdevice.
 15. The wireless device of claim 14, wherein the determining tosend a report of a channel estimate depends on one or more of: i) abuffer status in the wireless device, ii) an estimate of a geographicmobility of the wireless device, iii) a value of a feedback controlfield in the first message, iv) an estimate of a cumulative networkactivity of the wireless device, and/or v) an estimate of an arrivalrate of received data at the wireless device.
 16. The wireless device ofclaim 15, wherein the cumulative network activity is a sum of a receivedpacket rate and a transmitted packet rate.
 17. A method comprising: byan access point (AP): sending a message to a first wireless device;receiving, from the first wireless device, a first channel report basedon the message; receiving, from a second wireless device, a secondchannel report based on the message; allocating a multiple accessresource based on the first and second channel reports, wherein thefirst and second channel reports are not scheduled by the AP.
 18. Themethod of claim 17, wherein: i) the first channel report comprises afirst received signal strength indication (RSSI) value, and ii) thesecond channel report comprises a second RSSI value.
 19. The method ofclaim 18, further comprising: transmitting a trigger frame to the secondwireless device, wherein: i) the multiple access resource comprises aresource unit (RU), and ii) the trigger frame comprises an assignment ofthe RU to the second wireless device.
 20. The method of claim 19,further comprising: receiving, from the second wireless device inresponse to the trigger frame, a physical layer convergence protocol(PLCP) protocol data unit (PPDU), wherein at least a portion of the PPDUis received over the RU.